Make the image loading code more modular

[libs/gui.git] / source / graphics / png / pngloader.cpp

diff --git a/source/graphics/png/pngloader.cpp b/source/graphics/png/pngloader.cpp
new file mode 100644 (file)
index 0000000..8553065
--- /dev/null
+++ b/source/graphics/png/pngloader.cpp
@@ -0,0 +1,94 @@
+#include <png.h>
+#include "pngloader.h"
+
+using namespace std;
+
+namespace {
+
+void read(png_struct *png, png_byte *data, png_size_t size)
+{
+       Msp::IO::Base *in = reinterpret_cast<Msp::IO::Base *>(png_get_io_ptr(png));
+       in->read(reinterpret_cast<char *>(data), size);
+}
+
+void error(png_struct *png, const char *msg)
+{
+       string *message = reinterpret_cast<string *>(png_get_error_ptr(png));
+       *message = msg;
+       longjmp(png_jmpbuf(png), 1);
+}
+
+} // namespace
+
+
+namespace Msp {
+namespace Graphics {
+
+struct PngLoader::Private
+{
+       std::string message;
+       png_struct *png;
+       png_info *info;
+};
+
+PngLoader::PngLoader(IO::Base &io, const string &sig):
+       priv(new Private)
+{
+       priv->png = png_create_read_struct(PNG_LIBPNG_VER_STRING, &priv->message, error, 0);
+       priv->info = png_create_info_struct(priv->png);
+
+       // These probably won't give any errors
+       png_set_read_fn(priv->png, &io, read);
+       png_set_sig_bytes(priv->png, sig.size());
+}
+
+PngLoader::~PngLoader()
+{
+       png_destroy_read_struct(&priv->png, &priv->info, 0);
+       delete priv;
+}
+
+bool PngLoader::detect(const std::string &sig)
+{
+       return !png_sig_cmp(reinterpret_cast<png_byte *>(const_cast<char*>(sig.data())), 0, sig.size());
+}
+
+void PngLoader::load(Image::Data &data)
+{
+       if(setjmp(png_jmpbuf(priv->png)))
+               throw bad_image_data(priv->message);
+
+       png_read_info(priv->png, priv->info);
+       png_uint_32 width;
+       png_uint_32 height;
+       int depth;
+       int color;
+       png_get_IHDR(priv->png, priv->info, &width, &height, &depth, &color, 0, 0, 0);
+       data.width = width;
+       data.height = height;
+       if(depth!=8)
+               throw unsupported_image_format("depth!=8");
+       switch(color)
+       {
+       case PNG_COLOR_TYPE_PALETTE:    data.fmt = COLOR_INDEX; break;
+       case PNG_COLOR_TYPE_GRAY:       data.fmt = LUMINANCE; break;
+       case PNG_COLOR_TYPE_GRAY_ALPHA: data.fmt = LUMINANCE_ALPHA; break;
+       case PNG_COLOR_TYPE_RGB:        data.fmt = RGB; break;
+       case PNG_COLOR_TYPE_RGB_ALPHA:  data.fmt = RGBA; break;
+       default: throw unsupported_image_format("unknown color type");
+       }
+
+       unsigned nchans = png_get_channels(priv->png, priv->info);
+       if(nchans==4 && data.fmt==RGB)
+               png_set_strip_alpha(priv->png);
+
+       unsigned rowstride = data.width*nchans;
+       data.data = new char[rowstride*data.height];
+       for(unsigned y=0; y<data.height; ++y)
+               png_read_row(priv->png, reinterpret_cast<png_byte *>(data.data+rowstride*(data.height-1-y)), 0);
+
+       png_read_end(priv->png, 0);
+}
+
+} // namespace Graphics
+} // namespace Msp